1.   After the floods, contaminated water was a serious threat to public health.

2.   Bad air quality poses a serious threat to public health.

3.   Chemicals in our drinking water could pose a serious threat to public health.

4.   Decide whether the pest is a serious threat or merely a nuisance.

5.   Global warming poses a serious threat for the future.

6.   His testimony presented a serious political threat to the incumbents on the city council and alienated Leroy from their affections.

7.   I have always found such liaisons a serious threat to the order in a house.

8.   In the developed world, over-consumption is now a serious threat to health.